Acceleration of vulcanization of rubber



Patented Aug. 11, 1931 UNITED STATES PATET ()FFICE JAN TEPIPEMA, OFAKRON, OHIO, ASSIGNOR TO THE GOODYEAR TIRE 85 RUBBER COMPANY, OF AKRON,OHIO,

A CORPORATION OF OHIO ACCELERATION or VULGANIZATION or RUBBER NoDrawing.

My invention relates to methods of vulcanizing rubber, and it has,forits primary object, the provision of a new class of materials adaptedto accelerate or promote the rate of vulcanization when incorporated ina rubber compound.

More specifically, my invention has for one of its objects the provisionof an improved accelerator which is composed of the reaction product ofmercaptoarylthiazoles having substitutions made in the aryl ring andamino compounds.

It has been observed heretofore that many thiazole compounds could beemployed as accelerators of the rate of'vulcanizatio'n of rubberwith-excellent result-s. Among the first compounds of this classdiscovered was mercaptobenzothiazole, which may be representedstructurally as follows:

Q I i I d-sn The numerals applied to various atoms'indi- J cate theposition of the atom in the molecule.

More recently it has been discovered that substitutedmercaptobenz'othiazoles, particularly'those containing substitutionsin'the aryl ring, also may be employed'as accelerators with excellentresults. Among such compounds 5-chlor mercaptobenzothiazol-e and 6-nitromercaptobenzothiazole are included.

45 toarylthiazoles having one or'more'hydrogen Application filed.November 21, 1927. Serial, No. 234,925.

atoms in the aryl ring replaced by heavier molecules, either negative orpositive, may also be made to react further with amines, either aryl oraliphatic, to produce double salts, which, when incorporated intoarubber -5o compound, very powerfully accelerate the vulcanizationthereof.

This class of accelerators includes the reaction products of5-chlor-mercaptobenzothiazole and diphenylguanidine,6-nitro-mercaptobenzothiazole and diphenylguanidine,6-amino-mercaptobenzothiazole and diphenylguanidine, chlormercaptobenzothiazole and diethylamine, 6-amido-mercaptobenzothiazoleand diethylamine and various other o similar substances.

The reaction product of 5-chlor-mercaptobenzothiazole anddiphenylguanidine' is particularly referred to and one method ofpreparing this material is as follows:

- Dissolve molecularquantities of 5-chlor- 'Idercaptobenzothiazole anddiphenylguanidine in separate solutions of alcohol, and then intermixthe solutions. Upon allowing the mixture to cool, the reaction productsep- 7-0 arates out as a crystalline product which may be filtered andwashed with alcohol and then dried. This material has a definite meltingpoint of about 17 4 to C. The fact that the material has a crystallinestructure, and '7 also a definite melting point, is convincing evidencethat a true chemical addition productis formed. The chemical equation bymeans of which the compound is formed may p be represented as follows:so

s r I NHCe s NHCcHa SH+NH=0 osNnF c Nnoun 01 NHUQHS '85 The methodoutlined above is not limited to the particular compounds justdiscussed, but may be employed to manufacture many other compounds ofthis class. For example, it may be employed to manuf cture the additionproduct of 6-nitro-mercaptobenzothia zole and diphenylguanidine6-amino-mercaptobenzothiazole and diphenylguanidine, etc. It has beenfound in the case of the reaction product of the nitromercaptobenzothiazole and diphenylguanidine that a purer compound isobtained by using double molecular quantities of the diphenylguanidine.The melting point of the reaction product obtained from these materialsis about 200 C, and the melting point of the reaction product of theamino niercaptobenzothiazole and diphenylguanidine is 168 C. Thesedefinite melting points indicate that, like the reaction product of-chlor-mercaptobenzothiazole and diphenylguanidine, thedatter reactionproducts are also definite chemical compounds.

Other methods tha-n thatjust discussed may be employed in themanufacture of certainreaction products of this class. TForeX- ample,the diethylamine salt 1 of 5chlormercaptobenzothiazole is most readilyprepared by causing the 'materials-td'react in an ether solution. In thereaction, about grams of 5-mercaptobenzothiazole are dissolved in 500cc. of dry ether. Drydiethylamine, prepared by "boiling commercialdiethylamine and conducting the vapor over potassium hydroxide is thenbubbled through the solution. -The reaction product of the 5-chlor-mercaatobenzothiazole and the diethylamineprecipitates out in they form ofWhite crystalline needles hav-ing-a definite melting point at 142 to 143C.

The reaction product of diethylamine' and -6amido-mercaptobenzothiazo-le may'ibe prepared by saturating a solutioncomposed of 10 grams of'6-amido-merca ptobenzothlaZole dissolved in 1100' cc. ofaniline vvith "drydiethylamine. The reaction productprecipitates in the form of a colorlesscrystalline material Whiclimeltsatab'out25t) to .ZGO (3., the lack-of shar anessotthe meltingpointbeingapparently due to-a decomposition of the reaction product. 4 r

The materials discussed may, oi course, be employed as accelerators ofvulcanization in most-of the standard rubber compounds. The following isan enample cilia-compound in Which theymay-be incorporated Wltll'QX-cellent results: s

Tl1c substances indicated in the following tables Were employed asaccelerators in this compound,'and the data obtained by subject '65 ingthe products obtained ''-to a tensile "20 min.

strength test are tabulated in conjunction therewith.

kgsJcrn. at 700% el.

Tensile Percent strength elongakgs/cm. tion Cure (1) Reaction product ofdiphenylguanidine with fi-chlormercaptobenzothiazole (M. P. 174175) 10min. at 205 i. min. at 2% (2) Reaction product of diphenylguanidine withG-nitro mercapto benzothiazole (M. P. 200) 4) Diethylamine saltor'c111or s tobesiotmmie1 MLrins 710 40 min. 660 min. 2'48 670 '50 min.15!) 650 min. i 750 40 min. ::62 z .310 60 min. I 40 84 825 0 m n. 1061'64 775 10 min. -130 182' 765 ever, all of the salts enumerated havevery.-

considerable poWeras :accelerators, and it is desired,therefore,=toinclude them in the scope of nay-invention.

My lnvention is: not limited merely to the reaction products ofmercaptoarylthiazoles containing substitutions in the aryl ring anddiphenylguanidine,.but also includes various reaction products of thethiazo-l'e-derivatives with other amines, both straightcchainhandaromatic.

I have disclosedaconsiderable :number *of substances of the sameclasswhich maybe regarded as substantially "equivalenttoeach other. Itevident, therefore, that my invention is not lim-ited to asinglesubstance, but includes a large class of related compounds,and myinvention should be broadly construed as includin all of thesecompounds. -Only such limitations should, therefore be imposed as areindicated by the appended claims.

WVhat-I claim is:

1. A method of vulcanizing'ru bbeiwvvhich comprises incorporating.a-reaction product of mereaptobenzothiazole containing 'basic iniinto avulcanizable rubber compound and heating the mixture thus formed.

2. A method of vulcanizing rubber which comprises incorporating areaction product of a mercaptobenzothiazole containing basic nitrogensubstituted for a hydrogen atom in the aryl ring and diphenylguanidineinto a vulcanizable rubber compounds, and heating the mixture thusformed.

3. A rubber product which has been vulcanized in the presence of areaction product of a mercaptobenzothiazole having a nitrogen containinggroup substituted for a hydrogen atom'in the aryl ring and asecondcarbon and hydrogen.

4. A method of treating rubber which comprises subjecting it tovulcanization in the presence of an accelerator having the formula inwhich R represents an inorganic group other than hydrogen and Rrepresents an amine containing only nitrogen, carbon and hydrogen.

5. A method of treating rubber which comprises subjecting it tovulcanization in the presence of an accelerator having the formula inwhich R represents a nitrogen containing group or a chlorine atom and Rrepresents a secondary aromatic amino group containing only basicnitrogen, carbon and hydrogen.

7. A method of treating rubber which comprises subjecting it tovulcanization in the presence of an accelerator having the formula inwhich R represents a nitrogen containing group or a chlorine atom and Rrepresents a secondary amine containing only basic nitrogen, carbon andhydrogen.

8. A method of treating rubber which co1n-- prises subjecting it tovulcanization in the presence of :an accelerator" having the formula. A.

in which R represents an amido group and vR represents a secondary aminegroup conslstlng of basic nltrogen, carbon and hydroized in the presenceofa material having the formula in which R represents an inorganicradical other than hydrogen and R represents an ary amine containingonly baslc nltrogen, amme group contammb only baslo n l carbon andhydrogen.

10.-A-,-rubberproduct that has been vulcanized in the presence of amaterial having in which R represents either a nitrogen containing groupor a chlorine atom and R represents a secondary amine group.

11. A rubber product that has been vulcanized in the presence of amaterial having the formula inwhich-R represents either a nitrogencontaining group or a chlorine atom and R represents a secondaryaromatic amine group containing only basic nitrogen, carbon andhydrogen.

12. A rubber product that has been vulcanized in the presence of amaterial having 1n which R represents either a nitrogen containing groupor a chlorine atom and R represents diphenylguanidine.

13. A method of vulcanizing rubber which comprises subjecting it tovulcanization in the presence of the reaction product of amidoanercaptobenzothiazole and diphenylguani- 14. A rubber product that hasbeen vulcanized in the presence of the reaction product of amidomercaptobenzothiazole and diphenylguanidine.

15. A method of vulcanizing rubber which 1 comprises subjecting it tovulcanization in the presence of an accelerator selected from a groupconsisting of the reaction product of diphenylguanidine and 5-chlormercaptcbenzothiazole, the reaction product of diphenylguanidine and6-nitro mercaptobenzothiazole, the reaction product of diphenylguanidineand G-amino mercaptobenzothiagen. Q p 9. A rubber product that has been.vulcanv henzothiaz ole; the

201e, fiche; diethyl amines saltizof chlorsmercaptobenzothiazole and thediethyl-amine: salt of G-amino mercaptobenzothiazole.

16. A rubber" product that has been Vulcam'zed in the presence of amaterial selected from wgroup consi'stiirgnf-the reaction produet of"diplieny-lguanidine and 5-chler merc-aptobenz'othiazole, the reactionproduct of diphenylguanidine and 6-nitr0 mercaptoreaction product ofdiphenylguanidine' and G amine mercaptobenzothiazole, the diethyl aminesalt of clilor mercaptobenzothiazoleand the diethylamine salt of6-a-mino mereapt'obenzothiazole.

In Witness whereof, I have hereunto signed may. name. r

$i'gned' at Akron, in the county of Summit; and State of Ohio, thisl9thday ofNovember,1927. I v W i JAN"TEPPEMA.

